1. Field of the Invention
The present invention generally relates to systems and methods for creating persistent data for a wafer and using persistent data for inspection-related functions. Certain embodiments relate to a system configured to store image data generated by scanning a wafer with an inspection system such that all of the image data or a selected portion of the image data generated by a detector during the scanning of the wafer is stored and can be used for one or more applications.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Fabricating semiconductor devices such as logic and memory devices typically includes processing a substrate such as a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. For example, lithography is a semiconductor fabrication process that involves transferring a pattern from a reticle to a resist arranged on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical-mechanical polishing (CMP), etch, deposition, and ion implantation. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.
Automated surface inspection is important to a number of different fields. For instance, inspection is substantially important when fabricating semiconductors to improve yields and provide process control. In particular, inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield in the manufacturing process and thus higher profits. Inspection has always been an important part of fabricating semiconductor devices. However, as the dimensions of semiconductor devices decrease, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause the devices to fail. For instance, as the dimensions of semiconductor devices decrease, detection of defects of decreasing size has become necessary since even relatively small defects may cause unwanted aberrations in the semiconductor devices.
Surface inspection is particularly challenging for semiconductor wafers in that the dimensions of structures present on the surface are extremely small and are continuously getting smaller as technology progresses. The size of the structures requires inspection systems to have extremely high resolution, which in turn translates to a substantially large amount of data collected during the inspection process. For example, the inspection of a single 300 mm diameter wafer may generate in excess of 3 terabytes of image data collected in 5 minutes or less when using current inspection systems such as the 2810 system, which is commercially available from KLA-Tencor, San Jose, Calif.
Because of the enormous amount of data generated by inspection, common practice is to design wafer inspection systems so that they process the acquired data rapidly since storing this amount of data would be either substantially expensive or practically impossible due to the underlying limitations of the technology used in the computers implementing the inspection algorithms. For example, current wafer inspection systems may utilize multiple processors (called nodes) with dedicated memory in each to distribute the computation load required to handle data streaming in from a sensor. This data may be partitioned into swaths across the wafer, and the swaths may be further sub-divided into sub-swaths, each sub-swath being processed by one node. The results of computation are passed to a host computer, and the memory of each node is cleared to make way for the data for the next (sub) swath. No “state” information about the previous scan is retained. In other words, the data from the sensor is discarded when the node reaches the end of the swath. As such, the node has no memory across scans.
Therefore, due to the large amount of data acquired, most wafer inspection has been implemented by providing image processing equipment capable of executing a defect detection algorithm at speeds matching those of the data acquisition apparatus. Executing the defect detection algorithm at such speeds often limits the complexity of the algorithm used. In particular, relatively simple algorithms may be used to ensure that the data is processed as fast as it is acquired. Alternatively, more complex defect detection algorithms that process data slower than the data acquisition rate may be used, but such algorithms require slower data acquisition thereby reducing the overall throughput of the inspection system.
Accordingly, it would be advantageous to develop systems and methods for creating persistent data for a wafer and using persistent data for inspection-related functions.